Fingerprint unlock: backoff time between retries

[Flohack74]

Currently Lomiri would try to read a fingerprint, and upon failure immediately retry, giving the user no chance to lift the finger. Also 3 retries is quite too low.
Implement a timer-based backoff that allows the user to correct finger position more easily, and also increase the max failed retries to 5.

[Flohack74]

Note that this PR introduces a change in behaviour (hence the changes to unit tests): When the fingerprint unlocking method is locked after 5 consecutive failures we no longer automatically emulate the swipe to get to the PIN or password input. I think this is very confusing.
In a second PR we will move up the hint text a bit from the very bottom, and also show a symbol if fingerprint scanner can be used or not.

[j2g2rp]

I've been testing this for last day on Volla x. Looks like Fingerprint reader works fine now.

[amartinz]

In a second PR we will move up the hint text a bit from the very bottom, and also show a symbol if fingerprint scanner can be used or not.

Is that plan documented somewhere trackable?

[Flohack74]

@amartinz yes currently here: #447